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Various models have been published calculating the light transport at the ocular fundus either for interpretation of in vivo reflectance measurements or for the prediction of photocoagulation effects. All these models took the absorption spectra of the pigments located at the ocular fundus, melanin, haemoglobin, xanthophyll, and the photoreceptor pigments,(More)
The purpose of this study was to measure the hemoglobin oxygenation in retinal vessels and to evaluate the sensitivity and reproducibility of the measurement. Using a fundus camera equipped with a special dual wavelength transmission filter and a color charge-coupled device camera, two monochromatic fundus images at 548 and 610 nm were recorded(More)
Longstanding diabetes mellitus results in a disturbed microcirculation. A new imaging oximeter was used to investigate the effect of this disturbance on retinal vessel oxygen saturation. The haemoglobin oxygen saturation was measured in the retinal arterioles and venules of 41 diabetic patients (65 ± 12.3 years) with mild non-proliferative through(More)
To determine whether visits or meals are the most biologically relevant unit of short-term feeding behavior, we analyzed 209,025 records of visits to feeders by 37 cows. Two feeds were used that differed in protein content. Cows were divided into control groups for the low and high protein feeds and a choice group that had access to both. Daily number of(More)
Imaging spectrometry is a new technique that permits simultaneous measurements of reflectance spectra at different locations along a line. Results are three-dimensional images, whose coordinates are location, wavelength, and reflectance. A conventional fundus camera is adapted to a spectrograph and an intensified charge coupled device (CCD) matrix detector(More)
A new model of the reflection of the human ocular fundus on the basis of the adding-doubling method, an approximate solution of the radiative transport equation, is described. This model enables the calculation of the concentrations of xanthophyll in the retina, of melanin in the retinal pigment epithelium and the choroid, and of haemoglobin in the choroid(More)
PURPOSE Luminance flicker stimulation of the photoreceptors is known to increase retinal blood flow. Elevated blood velocity was determined using laser Doppler velocimetry, and increased vascular diameters during flicker were observed by measurements with a retinal vessel analyzer. Oxygen supply may be the target of the regulation of retinal blood flow.(More)
The oxygen utilization and, therefore, the metabolic state, of a distinctive area of the retina may be calculated from the diameter of the supplying artery and vein, the haemoglobin oxygenation, and the velocity of the blood. The first two parameters can be determined by imaging spectrometry at the patients ocular fundus. However, the reflected light(More)
PURPOSE To determine alterations in the retina of patients with Alzheimer's disease (AD) by the newly developed technique of fluorescence lifetime imaging ophthalmoscopy (FLIO) in a pilot study. METHODS FLIO set-up uses a scanning laser ophthalmoscope (HRA2, Heidelberg Engineering, Germany), which was modified by the use of an excitation pulse laser(More)